Jace's Long Lost
by fortheloveofOTPs
Summary: Set right before CoHF, Jace comes to Magnus's one day to find a strangly familiar girl there, blonde hair, teal eyes, and so strangly familiar. he needs to know about her cryptic past, and the more she shrugs him off the more desperate he beocmes. but for Gemma is has turned into her worst nightmare. she has finally net her brother and will she be able to face up to the truth?
1. Chapter 1

Gemma choked back a sob as she struggled to lift up her Great-great-great Aunt Tessa and draw a portal at the same time. Tessa was a special breed of shadowhunter, born from an unmarked shadowhunter and a warlock, resulting in her not being born dead. She was also immortal, having stopped aging around the time she turned twenty. Tessa had cut herself out of the family after a generation, wishing to not see her great-grandchildren die as well, but Gemma was the exception, living full time with Tessa in their New Orleans home, acting as if Tessa were her dead mother's sister, not her father's, father's, mother's mother. Which she really was. Tessa and Will had a daughter amongst their other children, who gave birth to a son, who married a Lightwood and gave birth to another son, who happened to be Stephen Herondale, Gemma's father.

Gemma was a secret child. Her father, not accepting his second wife's death, had been more than happy when she suddenly showed up at his door three years later, taking him to bed. It was when she produced a child that Stephen freaked, taking his own life. The child, Gemma, was left alone on a doorstep in Idris, where a young warlock by the name of Magnus Bane had found her. Raising her, along with Tessa had been some of the happiest times of Magnus's life. But when things with Valentine and Jocelyn and Clary had gotten too complicated, Magnus had sent Tessa and young Gemma to New Orleans, where they had resided ever since she was four.

Against all odds of Stephen being a marked shadowhunter and his new found lover being a warlock, Gemma was born alive and well, perhaps due to some of Tessa's blood a ways up the bloodline. However, ever since their last visit to Idris, where Tessa and Gemma had fought together in the war against Valentine, things had gotten more complicated. Gemma had always known of her elder brother, Jace, but had chosen to not have anything to do with him. She had spoken briefly to him after the war, before Clary had shown up and she fled to find Tessa, but nothing more than that. Now she had nowhere else to go. It was either to Jace or to Magnus, and knowing that Jace was currently getting over from being under Sebastian's bidding and was probably with his girlfriend, Clary, Gemma felt she had made the obvious choice.

She finished drawing the portal, held tighter to Tessa's mauled body, and stepped through, thinking only of Magnus's place. Against all odds it worked. Gemma opened her eyes to see a pair of very familiar eyes staring back at her, the golden-green cat eyes of Magnus.

"Magnus!" she screeched. "It's Tessa! Please! I can't lose Tessa!"

Magnus jumped into action, picking Tessa up from off the floor. "God Gemma, what happened?"

"Shax demon," she managed to gasp, "she was trying to protect me."

Magnus nodded, ignoring the amount of blood seeping from Tessa and onto his brand new carpet. "Go get my kit from the box, the one you and Tessa put together years ago."

Gemma nodded, knowing what he meant. She sprinted out the room and into Magnus's, searching frantically through a large trunk to find the special first aid kit she and Tessa had jokingly made earlier.

"First aid for creatures like us!" Tessa had teased Gemma, who was only five at the time. They were sitting in their New Orleans home foyer, getting ready to ship the package off. "Now," Tessa continued, "we just create a portal, and ship it through!" the box whisked off and the portal snapped shut. "And now, it's time for chase!" Tessa had cried, as she jumped up and chased a little Gemma down the hall. Gemma shook the memory out of her head. She had to focus, where was that box?


	2. Chapter 2

Meanwhile, back in Magnus's kitchen where Gemma had portaled in Tessa was beginning to wake up. She gasped in pain as her eyes flew open, searching frantically for Gemma's face.

"Gemma!" she gasped, almost inaudible.

"Lie back down ," Magnus commanded. "you'll just hurt yourself."

"No!" Tessa cried, "Where is she! Magnus you must be worried, she is as much your child as she is mine!"

Alec stiffened at these words but said nothing, hurt at the amount of emotion Magnus showed at those words.

"Indeed she is but you must lay back Tess, she is fine."

Tessa relaxed a little but not much. "I know I am dying Magnus, and you must promise me that you will take care of her. She has grown up so much dear Magnus, she is Will alive again! I swear to it that she is Will alive again."

Magnus smiled sadly as a tear slipped down his cheek, "Of course, I will always look out for her. No doubt she is Will alive again, she was raised by you! But come on now, no more of talk of dying, besides, it's bad luck to talk that way around a sick person Tess, surely you haven't forgotten that over the years."

Tessa rolled her eyes in agreement and laid back down as Gemma came rushing into the room, carrying a small wooden box. She threw herself down next to Tessa and tore it open, handing Magnus one vile of potion after the other. When he found the right one he quickly uncapped it, dripping a bit into Tessa's wounds, and a bit into her mouth.

Gemma and Magnus sat as still as statues for a moment, until they saw Tessa take a breath, then another, steadier this time. Gemma sobbed with relief and fell into Magnus's arms.

"So sorry to bother you," she muttered into his chest.

Magnus gave a low chuckle. "No bother at all, my dear, and look, she is waking up. Nothing could keep Tessa away from you for long."

Gemma turned her head to see that it was true. She grabbed Tessa's hand but still remained well within Magnus's embrace. "Tessa? Aunty Tessa? Can you hear me?"

Tessa's grey eyes opened some, and she smiled, squeezing Gemma's hand. "You're not getting away from me so easily Gemma," Tessa joked.

Gemma gave a small laugh and went to sit by her, talking together quietly.


	3. Chapter 3

Magnus came over, having finished cleaned up, and offered to lift Tessa up and give her a room to rest in. Tessa complied but refused to take the one with hot pink and black décor. Magnus put her in the blue room, leaving Gemma the peach room she had always loved. She had always thought that if it weren't for Tessa and Gemma visiting so often in the early years, all Magnus's guest rooms would be as crazy as the last, and she always liked to think that he had kept them in their original colors in case she and Tessa ever decided to come back.

Magnus came back to find Gemma sitting on one of the couches with the other three staring at her. He could feel the tension in the air but to Gemma's credit she didn't back down. After all, she was special, mostly shadowhunter, with some warlock blood mixed in. Not enough for a warlock mark and not enough to do any true magic, but it was there.

Gemma jumped up when Magnus came in the room and ran over to hug him. Magnus hugged her back, relieved to be able to see her again after so many years.

"How is New Orleans?" he asked.

"Oh it is wonderful! I so understand now why you were banned from Peru, I mean of course-"

She was cut off by a glare from Magnus as he glanced up at the others.

"Ah, I mean you totally need to come live with us again. I miss having a Magnus around, and it's so boring without you. Plus, some days it's getting worse, Tessa will break into sobs. I think having me around with my Will face and attitude is too much."

Magnus shook his head, "Having you around is never too much, no matter who you remind her of. You could remind her of Jessamine and she would never falter."

Gemma smiled, "Thanks Magnus, but I don't know if I would want to be like Jessamine, I love shadowhunting too much!"

Magnus ruffled her hair and offered her something to eat.

"Some pancakes would be great," Gemma said, with a completely serious expression.

Magnus stared her down for a moment before throwing up his hands in forfeit. "Fine, but only this time Grey," as he went to make pancakes. Then he looked over at her with a weird expression on his face. "Are you still going by Tessa's last name?"

Gemma shrugged, she had to keep her real last name hidden, she already knew who she was, a Herondale, and she didn't need others mixing her up with Valentine. "I mean, I have been going to see Jem with Tessa for a couple of years now." She ignored the shocked expression on Magnus's face and continued on, "And he offered for me to have his, but I was thinking I'd just wait until the whole Valentine thing blows over, and it looks as though it might be close, but with Sebastian I have learned to never hope."

Magnus gave her a sad expression as he slid a plate of golden and fluffy pancakes towards her, topped with melted butter and runny syrup. Gemma was just taking her first bite when the front door flew open and in tumbled five young adults to older teenager tumbled in. One of them had a shock of dark black hair and bright blue eyes, 'A Lightwood,' Gemma recognized, he looked just like Cecily's boys that Tessa had described. Then came another girl, with the same face and hair as the boy but with darker eyes. She must be his sister. She was arm in arm with a boy who looked a year younger, and who had shockingly pale skin and dark eyes. Gemma recognized him as a vampire and stiffened, bu a vampire who hung out with shadowhunters? Unlikely. The last girl had firery red hair and bright green eyes and was arm in arm with him. Jace, her brother. He was here.


	4. Chapter 4

Gemma stiffened and turned to Magnus, accusingly, before turning back towards the new arrivals and fleeing the room.

Magnus looked over at the mob of kids and grumbled, "You really picked the wrong time to visit, but I should explain some things. Sit down."

Jace shook his head and pulled away from Clary. "Magnus, is that-" he stopped short, allowing Magnus time to nod, before sprinting after the girl who he knew was his sister.

Clary and the others looked on with confused faces, then at Magnus. Magnus looked up, sort of sheepishly. He was about to explain when he heard Tessa's voice coming from down the hall, "Magnus, I think Jem is coming."

Magnus cursed and pushed the teenage mob to the couch before running to the door, upon flinging it open he found Brother Zachariah standing silently in the door way. Tessa came around the corner and stopped short when she saw Jem in Silent Brother form.

"Zachariah," she said with a bow of her head.

Jem didn't say anything aloud but it was clear that he was speaking in her head. Tessa seemed to be able to do the same, and the two looked at if they were having a shout off. Suddenly Tessa burst out, "Well what do you want me to do?! I couldn't just keep her at the New Orleans institute, pretending to be a Grey, for the first year they all thought she was lying! No marks stay on her skin, and the London Institute is all I could take her too! Either that or to the Fairchild clan and the angel only knows where the disappeared to!"

Clary gave a little breath when she heard her real family name and Tessa spun on her. "You, girl, you look like a Fairchild. Short, red hair, yes I can see the easy resemblance. And you are an active shadow hunter."

Clary nodded, startled by her curt tone."But I go by Fray now."

Tessa made a sound with her tongue like she was chastising Clary, "Charlotte would not be happy to see that."

Magnus nodded, despite himself. "The things that woman believed in."

Tessa gave him a small smile before whirling on Jem again,  
having struck up their shouting match. Then with a whirl of his parchment colored cloak Jem stalked out of the apartment and Tessa slumped against the wall.

"I hate fighting with him."

"Wow," Alec spoke up, "I've never seen such emotion form a silent brother before."


	5. Chapter 5

**so guys, hope you're enjoying! and no, i dont own any of the mortal insturments or infernal devices characters. so please please review. i should have the next xhapter up soon! also, this contains some clockwork princess spoilers, sorry i didn;t say it sooner!**

When Gemma had fled down the fire escape after seeing her brother she had not known that Jace would follow her. But he did.

Down the fire escape, across the street, and through the maze of ally-ways until Gemma finally collapsed, sobbing, in an old and abandoned school yard, right near the river.

Jace walked with silent footsteps to her, and crouched down.

"Hey," he whispered.

Gemma jumped a foot in the air, and turned to run away again when Jace caught her arm.

"Don't run away again! I know I have seen you before, but I just can't place where. Please, _please, _I have to know."

Gemma nodded and sat down in the tall grass, motioning for Jace to sit next to her.

Gemma took a deep breath before starting her long winded story. "Okay, so it all started many years ago when your great-great-great grandfather, Will Herondale, married a girl named Tessa Grey. Tessa and Will had children, then they had children, who had kids, who had your father, Stephen."

She paused for a moment to see if Jace was following. He gave her a nod so Gemma continued on. "So Stephen, your father, married your mother, and the whole uprising with Valentine happened, you've heard of this, and you were taken from your mother and so forth."

Jace nodded, "Yes I understand all of that, but what does the whole history lesson have to do with you?"

"I'm getting to that part Jace. So after your mother died your father went berserk. He wouldn't speak to anyone but your dead mother, blabbering on and on and such. Eventually a demon came into play, posing as your deceased mother.

Stephen was so glad to see his supposed long-lost wife that they, you know, conceived a child."

"So you're telling me I have a sibling? Wait but no, offspring of demons and shadowhunters are stillborn. So why are you telling me this?"

"Patience Jace! Let me finish. Anyway, the reason I had brought up Tessa and Will is because Tessa was like this baby, born from an unmarked shadowhunter and a demon. Only Stephen wasn't unmarked, so the baby should have died. But they didn't. somewhere along the way Tessa's blood had reappeared, causing the baby to live.

Now Tessa, she is immortal, being a sort of Warlock and all that, so when Stephen realized what he had done, conceiving a living child with a demon, he left her out on the streets."

"Her?" Jace interrupted.

"Yes, this baby was a girl. So anyway, Tessa found her and decided to keep her, raising her up with another Warlock friend. But when things started going bad a couple years ago, rumors of Valentine, Tessa hid the girl and herself away."

"So you're telling me I have a sister, somewhere out there, being raised by a sort of Warlock, and my sister is also a sort of Warlock."

Gemma nodded. "Yes, most of that is true only no, your sister is not out in the world. In fact, she is right in front of you."


	6. Chapter 6 AN

**Hey guys this is just an authors note, im really sorry! i just had to say im really sorry for not updating, but i've been really working hard in schooling, trying to finish the year early and then i discovered Doctor Who and my life hasn't been the same. it is literally ruined, when ten regenerated i was a serious mess. and my friend got it all on video. i just know this will come back to haunt me. but anyway my mum and i are driving down to jazz fest this weekend so that's a long car trip that i will hopefully have a lot of time to write during! thanks so much for any of you who followed, reviewed, and favorited. please keep it up! Thanks guys!**


	7. Chapter 7

**sorry for the wait lovelies**

Jace stared at Gemma for a moment, before giving an accepting nod.

"That's all," Gemma asked, "you're just going to calmly accept the prospect of having a sister?"

Jace shrugged, "I mean you look nothing like me, but I've heard whispers, and I saw you at the battle with Valentine. Plus you just seem so incredibly familiar. Like I'm missing something that has really been in front of me this entire time, but I'm just too stupid to see it."

"Well not really in front of you, but down in New Orleans," Gemma admitted.

"New Orleans? But that's impossible; I was down there for a meeting just last winter. I couldn't have missed you."

Gemma shrugged, "The other shadowhunters down there don't really trust me, and Tessa tries to keep me under the wraps. Of course she wouldn't let me go flaunting about with my brother in town."

Jace nodded, "I guess that makes sense. So where will you live now?"

"Well, now that is quite the question. I've always wanted to move back in with Magnus, ever since living with him for a while when I was little, and now that you know about me there is really no danger in living in New York, and we even would have Tessa in Magnus's good care, so I really don't see any down fall to this."

"I'd like having my sister near me." Jace admitted his eyes downcast.

"Would you like to know more about our history?"

"Oh wow, yeah that'd be great, I don't really know anything about the Herondales."

Gemma nodded and laid back, staring at the darkening sky, twilight, her favorite time of night, when everything was washed in that beautiful blue like color. "Well Tessa, she's part shadow hunter, part warlock, but since her mother wasn't marked Tessa didn't die. Then she married Will Herondale, and Cecily, Will's sister, married a Lightwood. And the other Lightwood married a serving girl, but he loved her so they denied all those who held doubts and married happily."

Gemma went on to describe their entire family tree, adding new last names, how Tessa watched Clary's ancestors grow up, all the way down to when Joyclnn left the Circle. They talked until the sky grew pitch black and the stars popped out, what few there were over New York City. Gemma felt her throat grow raw with words and eventually she stopped talking, prompting Jace to begin his story. How he was raised by Michael for some time, then taken in by Valentine and taught the horrors of life. Gemma learned of Clary's past and her heart swelled with pride at the thought that Jace had found someone to love him completely and wholly as he loved her.

Gemma learned of the recent lost Max, and she regretted her decision to not contact her brother sooner, as she missed out on meeting this intelligent little boy. All too soon yet hours later Jace sat up.

"It must be past midnight, we should get going." He picked himself up off the ground and offered his hand down to Gemma, who gladly took it, her bones popping as she moved for the first time since lying on the grass. Gemma took in her surroundings and realized with a sinking feeling that in her blind run to get away from Jace she was now lost.

She looked up to Jace, who must have seen the hopelessness in her eyes for he took off to the right, calling back to Gemma "Catch me if you can!"

Gemma let out a laugh and took off at a sprint. Jace might be the one with the angel blood, but Tessa was part Warlock, and boy was she going to play that to her advantage. With a quick mumble of words she increased her speed, easily catching up and passing Jace.

"Hey that's not fair! No warlocky powers!"

"You're the one with the freak angel blood!" Gemma called back.

Lucky for Gemma she recognized where she was, and with one left turn and a final right she was at the corner where Magnus lived. Glancing up she could see that the window they left out was closed, Magnus's doing no doubt.

Jace caught up with her in no time, also seeing the window.

"Hey Jace," Gemma began casually, "how much you wanna bet that I can zap us into the apartment?"

"How about nothing at all?" Jace said warily.

"Oh come on brother, have a little faith!" With that Gemma gripped his hand tight and squeezed her eyes shut, concentration on the peach room in Magnus's apartment.

She heard a soft 'pop' and felt the walls of reality closing in on her before she opened her eyes to pitch blackness. Had it worked?

"Uh, Gemma," Jace asked, "could you possibly get off my leg? And where are we?"

"Wait, I think I found a door knob," Gemma said, twisting it open. The pair stumbled out into the warmly lit hallway, and when Gemma looked back she saw that Magnus had painted one of the bathrooms peach. She was really going to have to be more specific in this Space Continuum hoping thing. She sat up and pulled Jace to his feet, about to speak when she heard the sound of someone clearing their throat behind her.

She whirled around to see six pairs of eyes staring at her and Jace. Flustered, Gemma said the only thing that came to mind, "Hello."


End file.
